1. Field of the Invention
The present invention relates to an information recording medium drive device, an information processing apparatus, a data replay control system, a data replay control method, and a computer program. In particular, the present invention relates to an information recording medium drive device, an information processing apparatus, a data replay control system, a data replay control method, and a computer program for preventing an unauthorized use of a content by effectively detecting an electronic watermark regardless of the type of data format.
2. Description of the Related Art
Currently, a variety of contents is available via networks such as the Internet, or in recording media such as compact disks (CDs), digital versatile disks (DVDs), mini disks (MDs). The contents may include audio data such as music, video data such as movies, game programs, and various application programs. The available contents may be replayed on personal computers (PC), or replay devices such as CD players, DVD players, MD players or game playing machines.
The distributorship of the majority of contents of the music data and the image data is typically held by a producer or a seller of the contents. A certain limitation is imposed on the distribution of the contents, in other words, an authorized user only has the right to use the corresponding content, and unauthorized copying of a content is typically inhibited.
Digital recording apparatuses and recording media are currently in widespread use. Such a digital recording apparatus and a digital recording medium allow a movie or audio to be repeatedly recorded or replayed without any quality drop involved. Use of an unauthorized copied contents becomes a concern.
Recently developed recording media, such as a DVD, can digitally record a large amount of data as large as a single movie in one piece of media. To protect copyright of a content from unauthorized copying becomes more and more important considering that video information is easily recorded as digital information.
Unauthorized copying of movie contents actually happen. High-definition digital video cameras and high-definition digital video recorders are expected to be commercialized for consumer market. If the problem of copyright protection is left unresolved, the benefits of copyright holders will be seriously damaged.
The content scramble system (CSS) is used as a copyright protection technique in the DVD disk storing video contents. The use of the CSS is permitted on the DVD-ROM media only. The CSS contract prohibits the use of the CSS on recording type DVDs such as DVD-R, DVD-RW, DVD+R, and DVD+RW. The CSS contract does not permit a bit-by-bit copying from a DVD video disk to a recording type DVD disk.
Even deCSS software programs for decrypting the CSS encryption are distributed over the Internet. One can get easily such a deCSS software program, decrypt the code of a DVD and write the DVD content onto a recording type DVD in a plain text.
Available as a means for preventing unauthorized copying is an electronic watermark (WM). Copyright information such as copy protection information is embedded as an electronic watermark in a content such as video or audio. An apparatus that replays or records a content detects the electronic watermark from the content, and performs control based on electronic watermark information, thereby preventing unauthorized copying.
Referring to FIGS. 1A and 1B, a content replay control process using the electronic watermark is now discussed. FIG. 1A illustrates an arrangement for detecting the electronic watermark in a MPEG bit stream, and FIG. 1B illustrates an arrangement for detecting the electronic watermark from a baseband signal subsequent to MPEG decoding.
As shown in FIG. 1A, a DVD decoder 112 performs a decryption process (ECMA-267, for example) on a DVD-ROM video disk 111 storing a video content in a DVD format, and a decryptor 114 decrypts the video content using a key detected by a key detector 113.
The decryption process performed by the decryptor 114 includes a descrambling process for CSS scrambling. The key detector 113 acquires the key for descrambling from the DVD-ROM video disk 111. The content stored in the DVD-ROM video disk 111 is not limited to the one encrypted with not only CSS but also other encryption method. The key detector 113 acquires a key applicable to the decryption of the encrypted content stored in the DVD-ROM video disk 111. Using the acquired key, the decryptor 114 decrypts the content, and outputs an MPEG-2 bit stream.
The MPEG-2 bit stream acquired by the decryptor 114 is subjected to an MPEG-2 decode process (such as ISO-13818) in an MPEG-2 decoder 115, while also being subjected to an electronic watermark detection process in the electronic watermark detector 116.
The electronic watermark detected by the electronic watermark detector 116 includes copyright information such as copy protection information, copy permission information, and replay permission information. The copyright information is embedded as bit data in the MPEG-2 bit stream. The electronic watermark detector 116 detects copyright management information as the electronic watermark information embedded, thereby outputting the copyright management information to a replay controller 117.
In accordance with the copyright management information input from the electronic watermark detector 116, the replay controller 117 performs a replay control of the decoded content input from the MPEG-2 decoder 115.
FIG. 1B illustrates the arrangement for detecting the electronic watermark from the baseband signal subsequent to the MPEG decoding. The difference between the arrangement shown in FIG. 1B and the arrangement shown in FIG. 1A is that the electronic watermark detector 116 detects the electronic watermark from the baseband signal subsequent to the decoding process of the MPEG-2 decoder 115 in the arrangement shown in FIG. 1B.
In the arrangement shown in FIG. 1B, the electronic watermark detector 116 detects the electronic watermark from the baseband signal. Like in the arrangement shown in FIG. 1A, the electronic watermark information detected includes copyright management information such as copy protection information, copy permission information, and replay permission information. The copyright information is embedded as bit data in the baseband signal. The electronic watermark detector 116 detects copyright information as the electronic watermark information embedded, and outputs the copyright management information to a replay controller 117.
The replay controller 117 performs replay control on the decoded content input from the MPEG-2 decoder 115 based on the copyright information input from the electronic watermark detector 116.
The appearance of the deCSS software programs is based on the fact that the key used by the decryptor 114 of FIG. 1 was broken. More specifically, key data was deciphered by reverse engineering a DVD player software program, and the entire CSS algorithm was finally deciphered after successive deciphering steps based on the broken key.
When the copyright protection technique such as the CSS is applied to an application program on a PC, tamper resistance is also typically included to shield the copyright protection technique from analysis. There is no measure indicating the strength of the tamper resistance. At what level the tamper resistance against reverse engineering is implemented is left to each implementer's own experience and performance. Finally, the CSS was deciphered.
Since people are concerned with security problem on the PCs, the effectiveness of the electronic watermark detection on the PC is also in question. The problem is the ease of reverse engineering of any program running on the PC, which is an open architecture.
In one of the proposed techniques, electronic watermark information is detected in a drive, which is easier to configure in black box than the PC.
Referring to FIGS. 2A and 2B, arrangements of detecting the electronic watermark information in a drive are discussed. FIG. 2A illustrates a storage process of an content and an electronic watermark onto a DVD-ROM, and a replay process of the DVD-ROM. FIG. 2B illustrates a control mechanism in which a content is copied to a DVD-R from a DVD-ROM, and the copied content is then replayed.
As shown in FIG. 2A, an watermark embedder 133 embeds watermark (WM) information 132 containing copy never information, for example, into a content 131 such as a movie, and a CSS scrambler 135 scrambles the content using a predetermined CSS key 134. A content stored DVD-ROM 136 thus results. An MPEG-2 encoding process (not shown) is performed as a pre-phase prior to the content scrambling process. Subsequent to the scrambling process, an encoding process for a DVD format is performed before being recorded onto the DVD-ROM 136. These processes are typically performed in each of standard disk manufacturers.
A user may replay the content stored DVD-ROM 136 on a host apparatus such as a PC. The DVD-ROM 136 is loaded on a DVD drive 140 connected to the host 150. For example, the content is transferred from the DVD drive 140 to the host 150 through an AT Attachment with Packet Interface (ATAPI) for replay.
The ATAPI is used to connect a peripheral device such as a CD-ROM drive, other than hard disks, to an integrated drive electronics (IDE) interface or AT attachment (ATA) interface. The peripheral device is controlled by packetizing a command from SCSI and handing the packetized command over to the IDE interface.
The DVD drive 140 includes an electronic watermark detector 141 and a CSS authenticator 142. The electronic watermark detector 141 detects an electronic watermark from the DVD-ROM 136 if a CSS key applied to descrambling of the CSS scramble is detected from the content stored DVD-ROM 136. Based on the electronic watermark detection, the electronic watermark detector 141 outputs the content to the host 150 through the ATAPI. Before the transfer of the content, an authentication process is performed between the CSS authenticator 142 in the DVD drive 140 and a CSS authenticator 151 in the host 150 in accordance with a predetermined authentication sequence. The authentication is established on condition that the CSS authenticator 142 in the DVD drive 140 sends the CSS key to the CSS authenticator 151 in the host 150, and then the content is output.
A CSS descrambler 152 in the host 150 descrambles (decrypts) the content input from the DVD drive 140 using the CSS key input from the CSS authenticator 151. The MPEG2 decoder 153 performs an MPEG2 decode process on the content. The content is thus replayed.
FIG. 2B illustrates a control process in which the content is copied from the DVD-ROM to the DVD-R and the copied content is replayed.
A deCSS 162 is applied to a content from a DVD-ROM 161 to remove a CSS key 163. A copy content is thus descrambled into a plain text, which is stored onto the DVD-R 165. An electronic watermark 164 cannot be removed. The DVD-R 165 having this content stored still contains the electronic watermark 164 (containing copy never information).
The electronic watermark detector 141 in the DVD drive 140 detects the electronic watermark, conditioned on the acquisition of the CSS key, and outputs the content to the host 150, conditioned on the detection of the electronic watermark. The CSS key cannot be found from the DVD-R 165 from which the CSS key has already been removed. The electronic watermark detection process is not performed, and the content output process is not performed. The host 150 is prevented from replaying the content.
However, a variety of problems is pointed out in the incorporation of the electronic watermark detector in the drive. Radon access is possible on a unit smaller than a unit of video information or audio information. Write data and read data flows through a single ATAPI channel. The scale of a circuit for the detection of the electronic watermark is large and thus costly. Process time for detecting the electronic watermark presents difficulty in an attempt to reduce write time and read time of the drive.
Subsequent to a ripping operation such as the deSCC operation, a content may be subjected to a codec process such as MPEG-1 or QuickTime, different from MPEG-2, or may be subjected to an encryption process. In this way, the process of the electronic watermark detector in the drive for executing the electronic watermark detection process on the MPEG-2 bit stream is deactivated. It is also pointed out that an electronic watermark method particularly designed for a certain codec is also deactivated by modifying syntax of the codec.
The aforementioned drawback is discussed with reference to FIG. 3. A content, replayed (read) in an authorized fashion from a DVD replay apparatus 201 or a DVD drive 202, is input to a PC-A 210. The output of the DVD replay apparatus, which is analog data, is converted in digital data, and MPEG2 processed by video capturer and MPEG2 encoder 211 in the PC-A 210. The content input from the DVD drive 202 is a scrambled MPEG-2 bit stream. A DeCSS 212 in the DVD replay apparatus descrambles the content.
The output of the video capturer and MPEG2 encoder 211 and the output of the DeCSS 212 respectively become contents in MPEG-2 bit stream.
These MPEG-2 bit stream data are input to a CODEC converter 213 for conversion into encoded data different from the MPEG2. Alternatively, the MPEG-2 bit stream data may be input to an encryptor 214 for a private encryption process such as an encryption process that employs a general-purpose encryption process algorithm such as DES. The resulting data is then stored in a recording medium or transferred to another PC-B 230 via a network.
The CODEC converter 213 converts the bit stream data into encoded data such as of MPEG-1, MPEG-4, QuickTime, DiVX, RealVideo, Windows Media Video, JVT, ON2, etc. In many cases, an electronic watermark detector installed in a PC or a drive typically performs an electronic watermark detection process that is input data format dependent. The majority of currently available electronic watermark detectors detects an electronic watermark that is effective only if the input data complies with the MPEG2 format. The electronic watermark detection process cannot effectively function in data in formats other than the MPEG2 format.
The coded data other than the MPEG2 or encrypted data is stored in a recording medium such as a CD-R, a hard disk, or a DVD. A CD-RW drive, a HDD 222, and a DVD drive 223 are respectively connected to the PC-B 230 to read data therefrom. Alternatively, these drives may be connected to the PC-B 230 via a network such as Ethernet® 224.
These pieces of data are input to the PC-B 230 without any problem. An electronic watermark detector in the CD-RW drive 221 is unable to effectively function if data is not in the MPEG2 format. The DVD drive 223 determines that the data is the one not to be processed in the electronic watermark detection process, and outputs the data to the PC-B 230. The other drives, namely, CD-RW drive 221 and HDD 222 output data to the PC-B 230 as in standard data read operation. The data transfer using the network such as Ethernet 224 is also performed without any problem.
If the data input to the PC-B 230 is encrypted MPEG2 data, a decryptor 231 performs a decryption process corresponding to the encryption process performed by the encryptor 214 in the PC-A 210, and further performs an MPEG2 decoding process. If the input data is data such as of MPEG-1, MPEG-4, QuickTime, DiVX, RealVideo, Windows Media Video, JVT, ON2 or the like other than MPEG2, a CODEC decoder 232 decodes the encoded data.
A video capturer card 233 digital-to-analog converts the decoded data to be output to an output unit 240 such as a display, a loudspeaker, and the like.
A content, which must be replay controlled based on the copyright information such as copy control information embedded in the content as an electronic watermark, is converted into encoded data other than MPEG2. The MPEG2 data is stored in or transferred to a recording medium. In this way, the content is freely replayed without being subject to the replay control in accordance with the electronic watermark information.
Japanese Unexamined Patent Application Publication No. 2000-115727 discloses a copyright protection technique incorporating an electronic watermark in which a DVD drive correctly detects electronic watermark information embedded beforehand in video or audio information. According to the disclosure, an error status (not permitting reading and writing) is returned to a PC if unauthorized copying is detected based on the electronic watermark information from successively read contents. If the content is converted to data other than of MPEG2, or if MPEG2 data is stored in or transferred to a recording medium as encrypted data, the content is freely replayed without being subject to the replay control in accordance with the electronic watermark information.
Japanese Unexamined Patent Application Publication No. 2001-210013 discloses a method of detecting electronic watermark information in a DVD drive at low cost. According to the disclosure, the output of video and audio signal is stopped if unauthorized copying is detected. If the content is converted to data other than of MPEG2, or if MPEG2 data is stored in or transferred to a recording medium as encrypted data, the content is freely replayed without being subject to the replay control in accordance with the electronic watermark information.
Japanese Unexamined Patent Application Publication No. 11-176087 discloses a control structure of a drive and a decoder separate from the drive for decoding data input from the drive. The decoder detects an electronic watermark from the decoded data, and determines, based on the detection result, whether or not the data is an unauthorized copied content. The control structure is arranged on a PC side, and related process is dependent on the PC. It should be noted that the relatively low security level of the PC invites the appearance of the deCSS software program. An attempt to control the unauthorized copying with the electronic watermark can be outwitted.